linux-kernel - Re: [PATCH v3] thermal: rockchip: make temperature reporting much more accurate

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Message-ID: <54C07AD7.9020102@rock-chips.com>
Date:	Thu, 22 Jan 2015 12:21:43 +0800
From:	Caesar Wang <caesar.wang@...k-chips.com>
To:	Daniel Kurtz <djkurtz@...omium.org>,
	Caesar Wang <wxt@...k-chips.com>
CC:	Heiko Stuebner <heiko@...ech.de>, Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <edubezval@...il.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	linux-pm@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] thermal: rockchip: make temperature reporting much
 more accurate


在 2015年01月22日 12:01, Daniel Kurtz 写道:
> On Thu, Jan 22, 2015 at 1:29 AM, Caesar Wang <wxt@...k-chips.com> wrote:
>> In general, the kernel should report temperature readings exactly as
>> reported by the hardware. The cpu / gpu thermal driver works in 5 degree
>> increments,but we ought to do more accurate. The temperature will do
>> linear interpolation between the entries in the table.
>>
>> Test= $md5sum /dev/zero &
>> $while true; do grep "" /sys/class/thermal/thermal_zone[1-2]/temp;
>> sleep .5; done
>>
>> e.g. We can get the result as follows:
>>      /sys/class/thermal/thermal_zone1/temp:39994
>>      /sys/class/thermal/thermal_zone2/temp:39086
>>      /sys/class/thermal/thermal_zone1/temp:39994
>>      /sys/class/thermal/thermal_zone2/temp:39540
>>      /sys/class/thermal/thermal_zone1/temp:39540
>>      /sys/class/thermal/thermal_zone2/temp:39540
>>      /sys/class/thermal/thermal_zone1/temp:39540
>>      /sys/class/thermal/thermal_zone2/temp:39994
>>
>> Signed-off-by: Caesar Wang <wxt@...k-chips.com>
>> Reviewed-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
>>
>> ---
>>
>> Changes in v3:
>> Suggested-by Daniel Kurtz,
>> the check doesn't reject "code == 0xfff"
>> Fixed in rk_tsadcv2_code_to_temp(u32 code)
>>
>> Changes in v2:
>> Reviewed-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
>>
>>   drivers/thermal/rockchip_thermal.c | 32 ++++++++++++++++++++++----------
>>   1 file changed, 22 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/thermal/rockchip_thermal.c b/drivers/thermal/rockchip_thermal.c
>> index 1bcddfc..ce18007 100644
>> --- a/drivers/thermal/rockchip_thermal.c
>> +++ b/drivers/thermal/rockchip_thermal.c
>> @@ -193,19 +193,22 @@ static u32 rk_tsadcv2_temp_to_code(long temp)
>>
>>   static long rk_tsadcv2_code_to_temp(u32 code)
>>   {
>> -       int high, low, mid;
>> -
>> -       low = 0;
>> -       high = ARRAY_SIZE(v2_code_table) - 1;
>> -       mid = (high + low) / 2;
>> +       unsigned int low = 0;
>> +       unsigned int high = ARRAY_SIZE(v2_code_table) - 1;
>> +       unsigned int mid = (low + high) / 2;
>> +       unsigned int num;
>> +       unsigned long denom;
>>
>> +       /* No code available, return callback */
>>          if (code > v2_code_table[low].code || code < v2_code_table[high].code)
>> -               return 125000; /* No code available, return max temperature */
>> +               return rk_tsadcv2_code_to_temp(code);
> Isn't this an infinite recursion?

No, I think we can try check if it  is happened.
Maybe we can return a warning/error for it.
>>          while (low <= high) {
>> -               if (code >= v2_code_table[mid].code && code <
>> -                   v2_code_table[mid - 1].code)
>> -                       return v2_code_table[mid].temp;
>> +               if (code >= v2_code_table[mid].code &&
>> +                   code < v2_code_table[mid - 1].code)
>> +                       break;
>> +               else if (code == TSADCV2_DATA_MASK)
>> +                       break;
>>                  else if (code < v2_code_table[mid].code)
>>                          low = mid + 1;
>>                  else
>> @@ -213,7 +216,16 @@ static long rk_tsadcv2_code_to_temp(u32 code)
>>                  mid = (low + high) / 2;
>>          }
>>
>> -       return 125000;
>> +       /*
>> +        * The 5C granularity provided by the table is too much. Let's
>> +        * assume that the relationship between sensor readings and
>> +        * temperature between 2 table entries is linear and interpolate
>> +        * to produce less granular result.
>> +        */
>> +       num = v2_code_table[mid].temp - v2_code_table[mid - 1].temp;
>> +       num *= v2_code_table[mid - 1].code - code;
>> +       denom = v2_code_table[mid - 1].code - v2_code_table[mid].code;
>> +       return v2_code_table[mid - 1].temp + (num / denom);
>>   }
>>
>>   /**
>> --
>> 1.9.1
>>
>>
>
>

-- 
Best regards
Caesar Wang (王晓腾)
福州瑞芯微电子有限公司
Fuzhou Rockchip Electronics Co.Ltd
福建省福州市铜盘路软件大道89号软件园A区18号楼(350003)
Addr:No.18 Building, A District, No.89, software Boulevard Fuzhou, Fujian,PRC
Email:wxt@...k-chips.com
Tel:+86-591-83991906/07->8221


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